The present invention relates to an inrush current limiter device for limiting inrushing current to a connectable load comprising: at least one switchable IGBT (Insulated Gate Bipolar Transistor)-based limiter unit for selectively limiting the inrushing current, having at least one current limiting conductor element for limited leading of current, and at least an IGBT-based switch, whereby the IGBT(Insulated Gate Bipolar Transistor)-based switch (Q2) is used as well as a controlled current limiter and as a by-pass element, and at least one control device for controlling the IGBT-based switch, whereby the control device comprises at least one IGBT-based switch supply and means for realizing a smooth flank of an output signal at the selected conductor element.
The present invention further relates to a power factor control circuit connectable to and/or between a main fed and a load comprising: an AC/DC converter with a capacitive buffer unit, and an inrush current limiter device.
Such well known power factor control circuits and inrush current limiters are used in a wide application area, where a load operating at high level of power and/or voltage has to be protected from damages by inrushing current. Modern loads are optimized for maximum electrical efficiency by minimizing consumption of electrical power. Unfortunately, the changes made to improve the efficiency of the ballast reduce certain external electrical resistances. This gives rise to a new problem: the occurrence of a large inrush off-current upon the first application of electrical power. This inrush current flows as a main filter capacitor and the ballast charges to its steady state value. For lighting circuit that contains a multiplicity of ballasts, the combined magnitude of the inrush is potentially large enough to cause contact failure of the switching device due to arching and contact welding.
To protect the load from damage by inrushing current, special power factor control circuits having inrush current limiters, are used.
Well known power factor control circuits for loads usually comprise an AC/DC converter followed by an inrush current limiter comprising an IGBT based switch supplied by an IGBT gate supply. For controlling the IGBT-switch, especially for switching, complex integrated circuits are used. Classically, the inrush current at switch-on is limited by either a NTC (Negative Temperature Coefficient) resistor, or a power resistor, which is short circuited by a relay or an IGBT after switch-on. While a NTC is only usable for lower power levels around a few hundred Watts due to its power losses, a relay has a low loss but a lifetime that is limited. The use of IGBT-based switches is a good solution with low losses for use at several thousand Watts and a long lifetime, but the timing and speed of switching it from off-state to a on-state is very critical. If this happens too soon or too abruptly, the IGBT- switch will break down due to excess current and power dissipation at the moment of switch-on.
Some very complex circuits and driver have been worked out to handle this switching, with still possible failure at repeated switch-on and -off. Another drawback is, that the circuits for controlling the IGBT are very complex and susceptible to damages.
Furthermore, the power factor control circuit known by the prior art works abruptly and produces drop-outs during the start period of the load due to a lack of synchronization between the load and an upstream arranged buffer.